It has been known that an organic polymer comprising at least one reactive silicon-containing group in one molecule has a property of crosslinking by siloxane bond formation accompanied with, for example, hydrolysis of a reactive silicon group due to water etc. at a room temperature and accordingly giving a rubber-like cured product.
With respect to the reactive silicon group-containing polymer, a polymer having a polyoxyalkylene main chain or a polyisobutylene main chain are disclosed in Patent Document 1, Patent Document 2 and the like and have already been produced industrially and used widely for uses as a sealant, an adhesive, paint and the like.
The curable composition comprising an organic polymer having a reactive silicon group is cured using a silanol condensation catalyst and, generally, an organotin catalyst having a carbon-tin bond, such as dibutyltin bis(acetylacetonate), is widely used. However, in recent years, issues have been raised concerning the toxic features of organotin compounds and, therefore, the development of non-organotin catalysts has been awaited. In Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6 and Patent Document 7, there are disclosed tin carboxylate salts and other metal carboxylates salts as silanol condensation catalysts and, further, it is disclosed that the addition of an amine compound as a cocatalyst or promoter results in improved curability. Further, from the environmental stress viewpoint, substantially metal-free curing catalysts are favorable and Patent Document 8 discloses that metal-free silanol condensation catalysts can be obtained by using an amine compound and a carboxylic acid in combination. However, the use of the non-organotin catalysts raises the problem that the adhesiveness tend to be inferior as compared with the use of organotin catalysts.
Patent Document 9 and Patent Document 10 disclose a technology of taking off the luster of the cured product surface or improving the antistaining properties of such surface by adding an amine compound having a melting point of 10 to 200° C. However, Patent Document 9 and Patent Document 10 describe such amine compound as a flatting agent or a stain resistance improving agent but does not describe the function of the same as a silanol condensation catalyst but describe, in the example section, organotin compounds as such catalysts. On the other hand, Patent Document 11 discloses a technology of attaining improvements in recovery and creep resistance by adding a guanidine compound to a curable composition comprising a polyoxyalkylene polymer having a reactive silicon group and a tetravalent tin-based curing catalyst but gives no description of the guanidine compound functioning as a silanol condensation catalyst.
Thus, in spite of the fact known in the art that such various physical properties as curability, stain resistance and recovery can be improved by adding an amine compound to a curable composition comprising a reactive silyl group-containing organic polymer, there are very few disclosures about a catalyst system in which an amine compound is used singly as a silanol condensation catalyst. Patent Document 12 discloses that an aryl group-substituted biguanide compound such as 1-(o-tolyl)biguanide, which is one species of amine compounds, acts as a silanol condensation catalyst. Patent Document 13 discloses that DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), triethylamine and the like serve as silanol condensation catalysts.
The present inventors used guanidine compounds having an aryl group bound to a nitrogen atom thereof, such as the aryl-substituted biguanide compounds described in Patent Document 12, as silanol condensation catalysts for reactive silyl group-containing organic polymers and encountered a problem that such compounds sometimes show no sufficient catalytic activity. Further, when they used DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), triethylamine and the like described in Patent Document 13 as silanol condensation catalysts, a problem arose, namely the cured product surface, when touched by the hand, stains the hand due to the movement of an amine compound-derived liquid compound to the cured product surface, that is bleeding out. Another problem encountered by them is that sometimes any practical curability or adhesiveness cannot be secured.
Patent Document 1: Japanese Kokai Publication Sho-52-73998
Patent Document 2: Japanese Kokai Publication Sho-63-6041
Patent Document 3: Japanese Kokai Publication Hei-5-39428
Patent Document 4: Japanese Kokai Publication Hei-9-12860
Patent Document 5: Japanese Kokai Publication 2000-313814
Patent Document 6: Japanese Kokai Publication 2000-345054
Patent Document 7: Japanese Kokai Publication 2003-206410
Patent Document 8: Japanese Kokai Publication Hei-5-117519
Patent Document 9: Japanese Kokai Publication Hei-9-100408
Patent Document 10: Japanese Kokai Publication Hei-11-193343
Patent Document 11: Japanese Kokai Publication 2004-83805
Patent Document 12: Japanese Kokai Publication 2005-248175
Patent Document 13: International Publication WO2004/022618